Physiology Motility Flashcards
Name the muscle layers and functions. What is the name of the motility program?
Muscularis mucosae - surface area
Circular muscle - reduce diameter
Longitudinal muscle - shorten
Muscle program is peristalsis.
Explain how smooth muscle generates contractions.
Spontaneous activity via pacemaker cells.
Slow waves to get to threshold. This generates an AP and leads to contraction.
What else affects smooth muscle contractions?
Modified/co-ordinated by stretch, nerves, hormones, reflex loops (e.g. enterogastric)
Describe what happens with motility in the GI tract.
Moves food through the GI tract Mechanical breakdown of food Mixing Contact Contraction/relaxation of smooth muscle
Why must motility be adaptable?
Due to the presence/absence of food
Type/amount of food
Absorptive capacity
Name the motility patterns.
Between meals - inter-digestive motor cycle
In presence of food - peristalsis and segmentation
Describe the features of the inter-digestive motor cycle.
Housekeeping - between meals Coordinated Migrating motor complex Clears cells, food secretions Enteric NS Motilin
What is the Migrating Motor Complex (MMC)?
Part of the inter-digestive motor cycle (between meals)
Co-ordinated - stomach –> small intestine –> large intestine
Describe the timing of the Migrating Motor Complex.
4-5 hours after a meal
Repeated every two hours
Name the three periods of the Migrating Motor Complex.
Inactivity
Intermittent activity
Intense activity
Where does peristalsis occur?
Oesophagus, stomach, SI, LI
How does peristalsis work and what is its function?
Proximal squeeze, distal relax
Ensures propulsion of food and mixing
Where does segmentation occur?
Small and large intestine
How does segmentation occur and what is its purpose?
Contract/relax the circular muscle (alter diameter size) leading to mixing and contraction of food.
What is the function of the mouth in the GI system?
Mastication/chewing
Reduces the size of food, mixes the food and ensures taste
Voluntary with reflex control
